Viruses are well known to modulate the biomass, diversity and activity of microbial communities in many ecosystems. Yet, little remains known about their role in stream biofilms. Here, we leverage metagenomic data from sediment biofilms in 200 glacier-fed streams (GFS) around the world to unravel the diversity and biogeography of benthic dsDNA viral communities. Among the 50,000 unique viral contigs larger than 10 kbp that we identified, the vast majority are absent from public viral databases, underscoring their specificity to GFS. Similar to the host communities, most viral populations are sample-specific, with only a small fraction shared across all mountain ranges. This pattern, however, is strongly influenced by viral lifestyle: lysogenic viruses are significantly enriched among the widespread viral populations compared to the rare ones. Spatial location was the primary factor shaping differences among viral communities, with strong regional patterns consistent with the expectation that viral exchange between distant, isolated sites is rare. More unexpectedly, we also detected a clear hemispheric signal: the seven mountain ranges in the Northern Hemisphere formed a distinct cluster from the four in the Southern Hemisphere. Proximity to glaciers further influenced viral community structure, with the Viral-to-Microbe Ratio (VMR) increasing significantly in samples collected closer to glacial fronts. The GFS microbiome shows low cell abundances and a few, well-adapted bacterial clades, reflecting adaptation to the extreme habitat. The correlation between VMR and glacier influence suggests that viruses cope better with the cold, oligotrophic conditions than their hosts, whose viral defenses may be constrained by the need to prioritize basic survival. Ongoing analysis of the viral gene repertoire aims to identify signatures of these adaptive strategies. Taken together, our work highlights the co-evolutionary history of phages and their hosts in a cryospheric ecosystem, now threatened by climate change.